25. The buffers that have wide use are zwitterions. Which of the following substances NOT have zwitterionic form? (A) Potassium chloride (KCl) (B) N-tris[hydroxymethyl]methyl-2-aminoethane sulfonate (TES) (C) N-2-hydroxyethylpiperazine-N'-2-ethane sulfonate (HEPES) (D) 3-[N-morpholino]propane-sulfonic acid (MOPS)